Simplify the following expression: $z = \dfrac{a^2 - 7a + 6}{a - 1} $
Explanation: First factor the polynomial in the numerator. $ a^2 - 7a + 6 = (a - 1)(a - 6) $ So we can rewrite the expression as: $z = \dfrac{(a - 1)(a - 6)}{a - 1} $ We can divide the numerator and denominator by $(a - 1)$ on condition that $a \neq 1$ Therefore $z = a - 6; a \neq 1$